Many ordnance devices, such as projectiles, mines or bombs, require a fuze to detonate the device at the desired place and time. An important part of the fuze is the safety and arming device (S/A), which contains a group of explosive components called an explosive train. The explosive train may be in an out-of-line (safe) position or in an in-line (armed) position. When in the safe position, accidental initiation of any of the elements of the explosive train must not lead to detonation of the weapon. Conversely, when in the armed position, initiation of the explosive train must always lead to detonation of the weapon.
Prior art methods of safe/arming an explosive device consist of using mechanical devices or exploding bridgewire devices. The mechanical safe/arming devices physically interpose a barrier between the detonator explosive charge and the main charge of the weapon. Mechanical devices have several drawbacks in that environmental degradation over an extended storage period results in an increased failure rate. In addition, as weapon designs become more complex, the requirements placed on mechanical safe/arming devices have resulted in clockwork mechanisms which are large, expensive, complex, and thus more unreliable.
Exploding bridgewire devices have no primary explosive charge in the detonator. The bridgewire device initiates the main charge by providing a tremendous pulse of high voltage current to the bridgewire which causes the bridgewire to explode. This initiates a booster which in turn initiates the main explosive charge. Because the exploding bridgewire detonator does not contain any primary explosive, the detonator may be connected directly to a booster or the main charge without the necessity of a mechanical safing mechanism. The drawback of the exploding bridgewire detonator is that it requires an expensive high voltage power supply to provide the necessary current for exploding the bridgewire. This is not generally suitable for conventional ordnance.
A more suitable method of safe/arming modern weapons systems for high reliability and safety is the use of an explosive logic network interposed between the electronically actuated detonators and a booster charge which in turn detonates the warhead. The explosive logic network, such as that disclosed in U.S. Pat. No. 4,412,493, receives an input from the detonators and performs syntactical or ordered operations to verify that a valid input combination has been received by the detonators.
In conjunction with the explosive logic network disclosed in the aforementioned patent, a synchronous explosive logic clock, such as that disclosed in patent application filed Dec. 23,1981 and Ser. No. 333,608, is utilized to open a time window during which a set of theoretically identical detonators must fire. The synchronous explosive logic clock also examines the first detonation to determine whether or not it is premature before propagating the detonation to the explosive logic network. The explosive logic clock disclosed in the aforementioned patent application No. 333,608 uses a synchronous approach to absorb the variation in theoretically simultaneous detonations necessitating extensive explosive delay paths which dominate network design. The complex path design of the synchronous explosive clock requires that the network be mapped on more than one surface. The asynchronous approach of the explosive logic safing device of the subject invention, together with the explosive delay path disclosed in patent application filed July 2, 1981 and Ser. No. 279,643, allows a safe/arming device to absorb the variation in theoretically simultaneous detonations, referred to as detonator "jitter", without resorting to complex, multi-surface network designs.